# Ice crystallizes in hexagonal lattice. At the low temperature at which structure was determined the lattice constants were $a = 4.53A^{\large\circ}$ and C = $b = 7.41A^{\large\circ}$ .Calculate the no. of $H_2O$ molecules present in a unit cell. (Density of ice = 0.92g/cm)
$(a)\;2\qquad(b)\;3\qquad(c)\;4\qquad(d)\;5$